fixed lint error

Author: Exar04

cmd/nerdctl/namespace/namespace_test.go

@@ -20,11 +20,13 @@ import (
 	"encoding/json"
 	"testing"
 
+	"gotest.tools/v3/assert"
+
 	"github.com/containerd/nerdctl/mod/tigron/test"
 	"github.com/containerd/nerdctl/mod/tigron/tig"
+
 	"github.com/containerd/nerdctl/v2/pkg/testutil"
 	"github.com/containerd/nerdctl/v2/pkg/testutil/nerdtest"
-	"gotest.tools/v3/assert"
 )
 
 func TestMain(m *testing.M) {